1. Field of the Invention
This invention relates to rack and pinion gear devices. More specifically, the present invention relates to an apparatus for properly indexing the pinion to the rack during assembly.
2. Disclosure Information
Rack and pinion devices are commonly used to transform rotations of a pinion into translations of a rack. Electrical switches and mechanical selectors frequently employ a rack and pinion device. Commonly, operators use switch devices to select a single function from several optional functions. An example of such an application is a climate control system operated through a rotary switch as found in motor vehicles. The operator selects an operating mode, such as "vent" from several options, such as floor, defrost, air conditioning, etc., by rotating the dial to the desired function. Another common motor vehicle application is the ignition key switch.
A problem in assembling switches employing rack and pinion devices is properly aligning the pinion to the rack. Alignment is difficult because the rack and pinion are meshed in a "blind spot," meaning that it is difficult to visually inspect the meshing. If the rack and pinion are not meshed properly during assembly, when the operator makes a selection, the desired function may not be activated. For example, when the ignition key is rotated to the "LOCK" position, the switch may actually engage the "ACCESSORY" position. When the apparatus is assembled in this condition, the switch is "misstaged." Preventing misstaging requires meticulous alignment during assembly, a time and labor intensive procedure. Ultimately, misstaging can result in a dissatisfied customer and increased warranty costs associated with removal and realignment of the switch.
Various devices have been proposed for indexing a rack and pinion. For example, U.S. Pat. No. 2,410,643 discloses a rack and pinion mechanism that provides self alignment for longitudinally engaging mechanisms. Longitudinal engagement occurs when the relative motion between the rack and pinion is on the longitudinal axis of the rack. This is not helpful, however, when the rack and pinion are engaged laterally, particularly in a blind spot. Lateral engagement occurs when the relative motion between the rack and pinion occurs generally perpendicularly to the longitudinal axis of the rack.
It would be desirable to provide an apparatus that would ensure accurate staging of a rack and pinion mechanism in which the pinion laterally engages the rack in a blind spot. It would be further desirable to provide a device that prevents a switch assembly from being assembled in a misstaged condition.